With the rapid development of the information industry, the desire for easily obtaining a hard color copy from the data terminal of an information processing device such as a computer, facsimile, etc., has increased. For meeting this desire, ink jet systems and heat-sensitive transfer systems have been investigated. However, ink jet systems have drawbacks in that since the system is performed by jetting an ink containing a coloring material through fine nozzles, the nozzles are liable to be clogged by the coloring material, etc., to reduce the reliability of recording. Also, heat-sensitive transfer systems involve imagelike heating and melting an ink on an ink sheet to transfer the ink onto a paper sheet, and hence for obtaining a color image of, for example, four colors, it is required to use four ink sheets, which is uneconomical. Also, in the case of the ink jet system, the user must always take care so that the ink does not become deficient, and in the case of the heat-sensitive transfer system, the user must always care so that the ink sheets do not become deficient. In other words, both systems compel the user to undertake a troublesome control of materials.
On the other hand, as a system which does not require such a troublesome control of materials and shows a high reliability of recording, a heat-sensitive coloring system is known and this system has recently been rapidly employed in the fields of black-and-white facsimile and for printers. In this system, a recording material composed of a support having thereon a layer having coloring mechanism and since the system is simple and convenient, the development of a multicolor heat-sensitive coloring system has been desired.
However, for realizing multicolor recording in the heat-sensitive coloring system, it is necessary to apply coloring mechanisms corresponding to the number of coloring colors on the same support together with function of controlling each coloring mechanism. Various efforts have hitherto been made, but the coloring control has so far been insufficient. Such efforts are described further below.
As recording materials for multicolor recording system, there are, for example, a recording material containing in the same heat-sensitive coloring layer a mixture of two kinds of coloring components coloring in different color hues at different coloring temperatures as described in Japanese Patent Publication No. 69/74 and a recording material composed of a support having formed thereon, in succession, a high temperature heat-sensitive coloring layer containing a coloring component coloring at a high temperature and a low temperature heat-sensitive coloring layer containing a coloring component coloring at a low temperature, as described in Japanese Patent Publication No. 19989/76, Japanese Patent Application (OPI) Nos. 88135/79, 133991/80, 133992/80 and 15540/73 (the term "OPI" as used herein refers to a "published unexamined Japanese patent application"). Furthermore, there is also a recording material having the above described high temperature coloring layer and low temperature coloring layer, further containing, associated with the low temperature coloring layer, an achromatizing agent, and showing an achromatizing effect with respect to the coloring component in the low temperature coloring layer at the portions corresponding to the colored portions of the high temperature coloring layer in the case of forming the images of the high temperature coloring layer as described in Japanese Patent Publication Nos. 17866/75, 5791/76, Japanese Patent Application (OPI) No. 161688/80.
However, these conventional multicolor heat-sensitive recording materials have various difficulties and are not satisfactory. For example, when low temperature and high temperature colored images having different color hues are formed by low temperature and high temperature printings using the recording material having on a support one or two heat-sensitive coloring layers, the color hue of the high temperature colored image causes color mixing with the hue of the low temperature colored image and the extent of color mixing changes when the printing conditions (the temperature, humidity and the kind of the printing machine) are changed, whereby images of a constant and stable color hue are not obtainable. Also, since at high temperature printing, regions having the same temperature as that of a low temperature printing are formed at the peripheral portions of the high temperature printing regions, a low temperature coloring occurs at the periphery of the high temperature printed image. This phenomenon is generally referred to as shading or bleeding (or ooze), which reduces the clearness of the images formed.
Moreover, in the recording material having an achromatizing mechanism, the occurrence of color mixing can be prevented, but the problem of causing color bleeding has not yet been solved.